c# - Where should exceptions been thrown? -

i have class looks following way:

public class stackoverflowquestion {      private string _question;      public string question {         { return _question;  }         set { _question = value; }     }      public stackoverflowquestion(string question) {         _question = question;     }      public override string tostring() {         return _question;     } } 

now, value "question" isn't allowed null or empty , user should notified via argumentnullexception - should been thrown? according 'fail-fast' principle -> everywhere.

public class stackoverflowquestion {      private string _question;      public string question {         { return _question;  }         set {             if(!string.isnullorempty(value))                 _question = value             else throw new argumentnullexception("value");         }     }      public stackoverflowquestion(string question) {         if(!string.isnullorempty(question))             _question = question;         else throw new argumentnullexception("question");     }      public override string tostring() {         if(!string.isnullorempty(_question)) return _question;         else throw new argumentnullexception("_question");     } } 

now ridiculous , extremely repetitive. seems right: if value set through .ctor, fails directly after short check. when set through property, fails directly after short check.. expects exceptions on setter? , when output string, expect string, not exception should have happend long ago, again: if it's wrong, should fail asap, if 'soon' quite late.

so, should exception handling been done? asking 'best-practice', or taste thing?

since _question private, there's no need check whether null in tostring() (unless you're sanity checking own code).

you can avoid check in constructor having constructor use property setter. thus, i'd recommend:

public class stackoverflowquestion {      private string _question;      public string question {         { return _question;  }         set {             if(string.isnullorempty(value))                 // make more transparent when thrown through constructor, might                 // preferable throw real error message "question: cannot null or empty"                 throw new argumentexception("value");            this._question = value;         }     }      public stackoverflowquestion(string question) {         this.question = question;     }      public override string tostring() {         return this.question;     } } 

a few things note: 1. should throw argumentexception rather argumentnullexception empty strings (if want can 2 checks , still throw argumentnullexception nulls). 2. while approach uses less code, 1 disadvantage error message users worse when pass null constructor, since failure happens 2 levels deep instead of one.